Nevoid basal cell carcinoma syndrome (NBCCS) is an autosomal dominant disorder characterized by bone and skin abnormalities and a predisposition to various tumors. Keratocystic odontogenic tumors (KCOTs), which are common tumors of the jaw that cause extensive damage to the jawbone, are usually accompanied with NBCCS. Germline PTCH1 mutations in NBCCS tumorigenesis have been frequently studied; however, little is known regarding the pathogenesis of bone abnormalities in this disease. This study sought to investigate the mechanism underlying heterozygous PTCH1 mutation-mediated abnormal bone metabolism in patients with NBCCS. Stromal cells were isolated from the fibrous capsules of patients with NBCCS-associated or non-syndromic keratocystic odontogenic tumors and non-syndromic tumor stromal cells without PTCH1 mutations served as controls. Germline PTCH1 heterozygous mutations were confirmed in all NBCCS samples and differential protein expression was identified using tandem mass tag-labeled proteomics analysis. Our findings revealed that osteonectin/SPARC expression was significantly downregulated in syndromic stromal cells compared with non-syndromic stromal cells. SPARC expression was even lower in stromal cells carrying PTCH1 protein truncation mutations. PTCH1 siRNA transfection demonstrated that SPARC downregulation correlates with decreased PTCH1 expression. Furthermore, exogenous SPARC promoted osteogenic differentiation of syndromic stromal cells with enhanced development of calcium nodules. In addition, bone mineral density tests showed that patients with NBCCS exhibit weak bone mass compared with sex-and age-matched controls. This study indicates that germline PTCH1 heterozygous mutations play a major role in bone metabolism in patients with NBCCS, in particular in those with PTCH1 protein truncation mutations. SPARC may represent an important downstream modulator of PTCH1 mediation of bone metabolism. Thus, bone mineral density monitoring is critical for patients with NBCCS for prevention of osteoporosis. In addition, surgical procedures on syndromic-associated KCOTs should be performed with consideration of the weaker bone mass in such patients.

Odontogenic keratocysts (OKCs) are common cystic lesions of odontogenic epithelial origin that can occur sporadically or in association with naevoid basal cell carcinoma syndrome (NBCCS). OKCs are locally aggressive, cause marked destruction of the jaw bones and have a propensity to recur. PTCH1 mutations (at ∼80%) are frequently detected in the epithelia of both NBCCS-related and sporadic OKCs, suggesting that PTCH1 inactivation might constitutively activate sonic hedgehog (SHH) signalling and play a major role in disease pathogenesis. Thus, small molecule inhibitors of SHH signalling might represent a new treatment strategy for OKCs. However, studies on the molecular mechanisms associated with OKCs have been hampered by limited epithelial cell yields during OKC explant culture. Here, we constructed an isogenic PTCH1R135X/+ cellular model of PTCH1 inactivation by introducing a heterozygous mutation, namely, c.403C>T (p.R135X), which has been identified in OKC patients, into a human embryonic stem cell line using the clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated 9 (Cas9) system. This was followed by the induction of epithelial differentiation. Using this in vitro isogenic cellular model, we verified that the PTCH1R135X/+ heterozygous mutation causes ligand-independent activation of SHH signalling due to PTCH1 haploinsufficiency. This activation was found to be downregulated in a dose-dependent manner by the SHH pathway inhibitor GDC-0449. In addition, through inhibition of activated SHH signalling, the enhanced proliferation observed in these induced cells was suppressed, suggesting that GDC-0449 might represent an effective inhibitor of the SHH pathway for use during OKC treatment.

Objective Odontogenic keratocysts (OKCs) are benign jaw lesions with high growth potential and propensity for recurrence. Our previous study revealed that PTCH1 mutations, which were frequently detected in sporadic OKCs, might be underestimated due to the masking effect of the stromal components within the tested tissues. We aimed to confirm these results in larger scale and further present the unbiased view of the genomic basis of sporadic OKCs except PTCH1. Materials and methods We analyzed PTCH1 mutations in additional 19 samples. Using whole‐exome sequencing (WES), we further characterized the mutational landscape of five sporadic OKC samples lacking PTCH1 mutation and loss of heterozygosity (LOH). Results Combined with our previously reported 19 cases, thirty of 38 (79%) cases harbored PTCH1 mutations. Through whole‐exome sequencing and integrative analysis, 22 novel mutations were confirmed among five PTCH1‐negative samples. No recurrent mutations were identified in the WES samples and validation cohort of 10 OKCs. Conclusions Our data further confirmed the frequent PTCH1 mutation and other rare genetic alterations in sporadic OKCs, highlighting the central role of SHH signaling pathway. In PTCH1‐negative cases, other rare mutations scattered in a subset of OKCs were independent of the SHH pathway. These results suggested that an SHH inhibitor may be effective to treat the majority of OKCs.

Objectives:The presentation-assimilation-discussion (PAD) class is a novel teaching method in which half the class time is allocated for the instructor's presentation and the other half for student's assimilation and discussion. This study evaluates and compares the teaching outcomes of the PAD class and traditional lecture-based method in oral pathology courses in School of Stomatology, Kunming Medical University. Materials and methods:The experimental and control groups included 88 undergraduates from Class 2017 and 72 undergraduates from Class 2016, respectively. The PAD method was applied on the experimental group in 2019, whereas the traditional lecture-based method was applied on the control group in 2018. The two groups' teaching outcomes were compared using final theory tests, biopsy diagnostic tests, and questionnaires. The Mann-Whitney U-test and independent-sample t-test were adopted for statistical analysis. Results:In five multiple-choice questions examining the same knowledge point from final theory tests, the distribution of the final scores showed a statistically significant difference between the two groups (p < 0.05). In the biopsy diagnostic tests, the experimental group scored higher than the control group (p < 0.05). In the questionnaires, there was no statistically significant difference for the "enhancing knowledge mastery" item (p > 0.05). However, the experimental group showed significant superiority in the remaining nine items (p < 0.05).